Preparing Salts Flashcards
Are nitrates soluble or insoluble?
Soluble
Are common chlorides soluble or insoluble?
Soluble, except silver chloride and lead chloride
Are common sulfates soluble or insoluble?
Soluble except lead sulfate, barium sulfate and calcium sulfate
Are common carbonates soluble or insoluble?
Insoluble except for sodium carbonate, potassium carbonate and ammonium carbonate
Are common hydroxides soluble or insoluble?
Insoluble except for sodium hydroxide, potassium hydroxide and calcium hydroxide
What are the two methods to creating a soluble salt?
- if it is a sodium, potassium or ammonium salt than react an acid with an excess amount of solid metal, metal oxide, metal hydroxide or metal carbonate
- Use a titration method/ indicator method. React and acid with an alkali (solution of sodium or potassium hydroxide or carbonate ( or ammonia solution) )
How do you make an insoluble salt?
- mix two solutions , one containing the correct positive ion and the other containing the correct negative ion.
Example- what two salts should i add to make lead sulfate?
- as lead sulfate is INSOLUBLE, you should react two SOLUBLE salts.
- lead nitrate and magnesium sulfate
Describe a precipitation experiment on how to make lead sulfate? ( with lead nitrate and magnesium sulfate)
- add one spatula of lead nitrate to a test tube and add deionised water ( to make sure there are no ions about) to dissolve it
- Shake thoroughly to ensure all the lead nitrate has dissolved
- In a separate test tube add one spatula of magnesium sulfate, add deionised water and shake to dissolve. ( same)
- Add the two solutions into a beaker and stir using a glass rod
- The lead sulfate should precipitate out
- Put a folded piece of filter paper into a filter funnel and still the funnel into a conical flask.
- Pour the contents of the beaker into the middle of the filter paper to not loose any contents.
- Rinse/swill out the beaker with more deionised water and tip it into the filter paper to make sure you have got all the precipitate from the beaker.
- Rinse all the contents from the filter paper with deionised water to make sure all the soluble magnesium nitrate has been washed away.
- Scrape the lead sulfate onto fresh filter paper and leave it to dry in an oven or desiccator.
Method of How to make a sodium, potassium or ammonium salt
Titration or indicator method
Method of How to make a not sodium, potassium or ammonium salt
- react an acid with an excess of a solid metal, metal oxide,hydroxide or carbonate
Common salts of potassium, sodium and ammonium
Soluble
Nitrates
Soluble
Common chlorides
Soluble except lead and silver chloride
Common sulfates
Soluble except lead, calcium and barium
Common carbonates
Insoluble except sodium, potassium and ammonium
Common hydroxides
Insoluble except sodium, potassium and calcium
Describe the method of the practical of making the soluble salts- use an acid and an insoluble base
- react acid that contains on of the ions you want in the salt with an insoluble base that contains the other ion you need ( often metal oxide or metal hydroxide)
-heat the acid in a water bath- speeds up the reaction between acid and the insoluble base in a fume cupboard to avoid releasing the fumes into the room - add the base to the acid- produce a soluble salt to neutralise it. You will know when the base is in excess and has been neutralised because the excess solid will sink to the bottom of the flask.
- filter off the excess solid to get a solution containing salt and water
- heat solution gently using a Bunsen burner or in a warm oven to evaporate off some of the water.
- allow solution to cool and allow the salt to crystallise
- filter off the solid salt and leave to dry
Practical method of making a soluble salt using a titration/inidcator reaction
- (reacting acid with alkali )
-measure set amount of acid into a conical flask using a pippette. - add a few drops of indicator ( colourless like phenolphthalein to have a clear colour change)
- slowly add alkali to acid using a burette until you reach the end point- when the acid has been exactly neutralised and the indicator changes colour.
- carry out the reaction using exactly the same volumes of alkali and acid but with no indicator, so salt wont be contaminates with the indicator - removes all the impurities
- solution that remains contains only salt and water
- slowly eva[prate off some water and then leave the solution to crystallise
- filter off the solid ad dry it- you will be left with a pure, dry salt
Why do you carry out a titration beforehand with indicator and another without it? In the practical of titration
- you can’t tell if the reaction has finished without the indicator- there is no signal that the acid has been neutralised. You cant just add an excess of alkali to the acid as the salt is soluble and it would be contaminates with the excess alkali. You need to find out exactly the right amount of alkali to neutralise the acid.
Example method of making a soluble salt by using an acid and an insoluble base to make a solution of copper sulfate
- add copper oxide to warm sulfuric acid to make a solution of copper sulfate
- you will receive hydrated copper sulfate
Why do you use deionised/ distilled water in the precipitate practical?
- to make sure there aren’t any ions- to remove all impurities and contamination to ensure it is a pure and dry salt
